Electric furnace



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ELECTRIC FURNACE Filed JulyA 5, 1938 9 Sheets-Sheet I5 Jan. 28, 1941. QF RAMSEYEVR 2,229,770

ELECTRIC FURNACE Filed July 5, 1938 9 Sheets-Sheet 4 INVENTOR d WerksZamsfyef' ,y MMAuw//JMATTORNE\S Jan. 28, 1941. C, F llaJflsEYEj--q2,229,770

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ELECTRIC FURNACE Filed July 5, 195e 9 Sheets-Sheet '7 huwdwnlzmlyfduaJan. 28, 1941. Q F' RAMSEYER 2,229,770

ELECTRIC FURNACE Filed July 5, 193. 9 Sheets-Sheet 8 y imm/fam m 141.2%,6

Jan. 28, 1941. c. F. RAMSEYER ELECTRIC FURNACE Filed July 5, 1938 9Sheets-Sheet 9 /fff Patented Jan. 28, 1941 UNITED STATES PATENT OFFICE 8Claims.

This application is a continuation-impart of my copending application,Serial No. 67,868, filed March 9, 1936.

The object and general nature of this invention is the provision of a.new and improved electric furnace especially adapted for use in but notnecessarily limited to the production of coal ash slag mineral Wool,whereby a product of improved quality and uniformity is secured. Bymineral woo is ordinarily meant a. line fibrous wool-like material, madeby blowing, drawing, spinning, or otherwise subdividing a small fallingstream of molten rock or other material, such as metallurgical slag, byany suitable means, so as to form bers or laments which solidify uponbecoming chilled.

The commercial form of rock wool in considerable use today is commonlymade by melting an argillaceous limestone in which the molecular rationof acid oxides (principally silica and alumina) to basic oxides(principally lime and magnesia.) is about one to one. The rock isquarried, transported to the plant, melted with coke in a cupola fromwhich the molten stream issues, and is then finally formed by suitablemeans into rock wool.

Instead of melting rock or the like, sometimes the slags resulting fromthe smelting of Various metallic ores, such as lead and copper, havebeen found to be suitable for remelting in a cupola and blowing into amineral wool, the product being usually referred to in this case as slagWool. Attempts to form the molten slags directly from the smeltersWithout cooling and remelting have commonly been unsuccessful, dueprincipally to a lack of control of the temperature and rate of iiow ofthe slag from the smelting furnaces.

Some of the other disadvantages encountered y in the production ofmineral wool by the processes mentioned above have been the high cost ofproduction and the difficulty of securing a uniform product. Not only isthe cost of production high, because the rock has to be quarried or theslag collected, the material transported to the mineral wool plant andrelatively expensive fuel (usually coke) purchased to melt the charge,but also, since practically the only method of controlling thetemperature, viscosity, and chemical content of the molten material isby changing the ratio of rock or slag to the coke charged in the cupolaor by varying the amount of material added to the charge, the control ofthe molten material and the mineral Wool formed therefrom is very farfrom being either instantaneous or automatic, since in most plants it isa matter of hours before the materials charged-in at the top of thecupola can influence the temperature or composition of the moltenmaterial coming from the tap hole.

One feature of this invention is the provision of new and improved meansby which the temperature, and more particularly the viscosity, of themolten stream of material from which the wool is formed can bemaintained continuously at the most advantageous point for the formationof the wool. A further feature of my invention having to do with themanufacture of mineral wool from a fused raw material is the maintenanceof the desired temperature and viscosity of the molten coal ash slag upto the point where the molten slag is delivered to the wool formingmeans, thereby insuring the production of mineral Wool f uniform qualityand character.

In this connection it should be mentioned that, as a part of the presentinvention, I make use of wet-bottom or slag-tap boilers or furnaceswhich have been developed within the last few years and are particularlyadapted to use pulverized coal. In boilers of this type the temperatureis kept high enough so that the ash of the coal collects on the floor ofthe boiler in a molten condition and can be drawn or tapped o at will,either continuously or at intervals as may be desired. Ordinarily, thepulverized coal is blown into the furnace, this method of firing beingparticularly advantageous with coals having a low fusion point ash, suchlow fusion point frequently being due to the presence of iron oxide inthe ash, the iron oxide being originally present in the coal, largely asiron disulfide or pyrites (FeSz) 'I'herefore, according to the presentinvention, I make use of the molten slag or ash-from furnaces of thistype, in which the slag or ash is relatively high in iron oxides, in theproduction of an improved mineral wool.

An additional object of the present invention is the provision of asmall furnace or container so constructed and arranged to receive themolten ash from the boiler plant, which may or may not be a Wet-bottomfurnace or the like, and to con trol the temperature and viscosity ofthe molten material so as to facilitate the subsequent formation of thesame into mineral wool. Such small or intermediate furnace, which may betermed a conditioning furnace, may be heated in any suitable manner,either by fuel or electricity-preferably the latter. According to theprinciples of the present invention, heat is generated in the molten ashby passing an electric current through it, whereby the molten ash itselfacts as the resistance in the circuit transforming the electric currentinto heat. By virtue of a conditioning furnace, the proper viscosity ofthe molten material may be maintained at all times for producing thebest quality of wool,

Another feature of my invention is the maintenance of the desiredViscosity by generating heat in the molten ash by passing an electriccurrent through it, whereby the molten ash itself acts as the resistancein the circuit transforming the electric current into heat andmaintaining substantially constant viscosity by maintaining theresistance of the molten slag substantially constant. This is possibledue to the fact that the viscosity of a molten oxide mass or mixture isdirectly related to its electrical resistivity.

It is recognized that the viscosity of the slag at the time the wool isformed is one of the most important variables determining the quality ofthe mineral wool, and thus by virtue of the present invention, whichcontemplates keeping the viscosity of the molten ash constant,variations in the chemical composition of the molten material whichordinarily would affect the quality of the wool are renderedsubstantially harmless.

Another feature of this invention is the -provision of a conditioningfurnace for maintaining molten coal ash slag vat the desired temperatureand viscosity point, and which is especially adapted for use withspinning disks instead of the more conventional steam jet apparatus forforming mineral wool from the molten slag.

Another feature of this invention includes improvements in theelectrodes of the conditioning furnace, whereby the maintenance ofconstant viscosity is facilitated.

These and other objects and advantages of the present invention will beapparent to those skilled in the art after a consideration of thefollowing detailed description.

In the drawings:

Figure 1 is a view showing a portion of the floor of a wet-bottom coalfired furnace and a portion of a conditioning or intermediate furnacereceiving the molten slag or ash from the wet-bottom furnace;

Figure 2 is a larger view of the intermediate or conditioning furnace;

Figure 3 is a section taken substantially along the line 3-3 of Figure2;

Figure 4 is a section taken substantially along the line 4 4 of Figure 3and showing the insulated cooling Water jackets and the electrically andthermally connected contact plates associated with the insulated coolingjackets;

Figures 5 and 6 are longitudinal and transverse sections taken throughthe roof of the conditioning furnace shown in Figure 2;

Figure 7 is an enlarged section taken vertically through one of theinsulated cooling jackets;

Figure 8 is a view illustrating one method of blowing the mineral woolby tilting the conditioning furnace about an axis substantiallycoincidental with the pouring spout of the furnace;

Figure 9 is a side view of another form of slag conditioning furnace;

Figure 10 is an enlarged fragmentary end view of the furnace shown inFigure 9, showing certain details of the water, gas and air connectionsfor the furnace of Figure 9;

Figure 11 is a side view of the furnace of Figure 9, with parts brokenaway to show certain details of the water-cooled electrodes;

Figure 12 is an end view of the furnace showing the electrodes inelevation and parts of the furnace water iacket in section;

Figure 13 is an enlarged section taken along the line I3I3 of Figure 12;

Figure 14 is a fragmentary end View, partly in section, of the furnaceshown in Figure 9; and

Figure 15 is a section taken along the line I5-I5 of Figure 14, showingthe dual slag spouts and their relation to the associated spinning disc.

Referring now more particularly to Figure 1, the coal fired boiler whichthe present invention makes use of is indicated in its entirety by thereference numeral I and includes more or less conventional water tubes 2and 3 and a floor 4 upon which the slag or` ashes from the combustion ofthe pulverized coal collect in molten state, as indicated at 5. Suchboilers or furnaces are provided with a slag hole 6, either in thebottom or side, through which the molten ash flows, more or lesscontinuously.

Boiler furnaces operate ordinarily at different rates at different timesof the day, and it is not practically possible in the operation of aboiler plant to operate the boilers under entirely constant conditions,due to fluctuations in the demand for steam. Hence it would be verydifficult to make a uniform quality of mineral wool from the molten ashjust as it is tapped directly from the boiler. I therefore tap it moreor less continuously into a small intermediate furnace or vessel ofwhich I can control the temperature, so that the bath of slag in thisintermediate or con` ditioning furnace is maintained at all times at theproper viscosity for producing the best wool.

The intermediate or conditioning furnace is indicated in its entirety bythe reference numeral III and includes suitable framework I2 carrying arefractory container I3, which will bel referred to in detail later,having a roof I4 in which a pouring opening I5 is placed. A trough I6 orthe like may be arranged for conducting a flow of molten ash from thefurnace I to the inlet openinf: I5 of the conditioning furnace IIJ. Ifdesired, there may be several conditioning furnaces I0 for eachprincipal boiler furnace I so that by shifting the trough or othersuitable means from one conditioning furnace to the other the continuousflow of molten coal ashes 5 may be accommodated.

Turning now to Figures 2 to 6, which best illustrate the details of oneform of conditioning furnace which has been found to be successful incarrying out the principles of the present invention, the furnace I0consists of end walls 20 and 2| and side walls 22 and 23, and a bottomwall 24 sloping downwardly toward a tap hole 25. The bottom, side andend walls are formed of refractory material, commonly employed wherehigh temperatures are encountered. The conditioning furnace may beheated in any suitable manner, either by fuel or electricity, but inorder to keep it as small as possible, I prefer to use elec tricity.Heat is generated in the slag by passing an electric current through it,whereby the slag itself acts as the resistance in the circuitvtransforming the current into heat. Since any slag containingappreciable quantities of iron oxide has an extremely corrosive actionon all known refractories, the side and end walls 20, 2|, and 22, 23 arewater jacketed so as to prevent overheating. The bottom 24 is not waiterjacketed but is more heavily lined with refractory brick or similarmaterial, due to the possible danger of the formation and collection ofmolten iron in the furnace. When iron does collect, the plug 26 (Figure3) may be removed and the molten iron drawn off through the slag tap 25.'I'he roof I4 of the furnace is also formed of refractory material, suchas re brick or the like, and is provided with the inlet or receivingopening I5, as best shown in Figures l and 5. It may be water jacketedif necessary. The water jacketing of the sides and ends of the furnacemay bev accomplished in any known manner, such as a. jacket 21 adaptedto contain water or other cooling medium and surrounding the ends andsides, with openings 28 and 29 for the jacketed electrodes; to bereferred to later.

According to the present invention, plate electrodes 3|, 32 and 33, 34are disposed on opposite side walls 22 and 23 of the furnace on theinside thereof and in the openings 28 and 29 in the furnace jacket 21.'I'hese plate electrodes are insulated from each other andare providedwith conducting bars 31 (Figure 7) which connect the plate electrodesboth thermally and electrically with the water jacket inserts indicatedat 40, 4|

and 42, 43. Refractory material is disposed between the plates 3|32, 33and 34 and the jackets 40, 4|, 42 and 43,`respectively, and the mass ofrefractory 44 relative to the mass of conducting bars 31 is soproportioned that the desiredrate of heat transfer between the coolingjacket and the electrode plate is secured, as will be explained mor'e indetail below.

The water jacket inserts are electrically insulated with respect to theother portions of the cooling jacket system, as best indicated in Figure7. In this gure the water jacket inserts 42 and 43 have insulatingstrips 45 and 46 secured to the upper and 'lower edges by bolts 49 and50, and the two Water jacket inserts at one side of the furnace, thusinsulated from one another, are bolted together as at 5| and to theupper water jacket 21 and a lower attaching plate 52 by bolrts 53 and 54(Figure 4). It is to be noticed that the conductor bars 31 connectingthe contact plates with the insulated water jacket inserts pass throughthe refractory material making up the side of the furnace. The bars 31are so proportioned .as to conduct heat from the contactor plate to thewater jacket at a predetermined rate sufficient to maintain the contactplates 3|, 32 and 33, 34 at a temperature low enough to preventdestruction by the molten material in the furnace. In other words, tomaintain the electrodes within the desired temperature limits, dependingon the viscosity required, the refractory material resists to acertainextent the flow of heat fromthe plates 3|,\32, 33 and 34 to theassociated water jackets, while the heat conducting bars 31 passingthrough the refractory material conduct a certain amount of heat fromthe inner plates to the outer Water jackets.

In any water cooled electrode, as long as there is any water in it atall, the temperature does not vary yto any great extent as com-paredwith the temperature of the molten slag, and therefore, according tothis invention, preferably I determine experimentally by trial in eachinstance the proper relative amounts and location of heat conductingmetal, and heat insulating refractory material which, combined, areinterposed -between the water cooling and the hot electricallyconducting electrode surface or contact plate to lengthen the life of.the latter but without chilling the molten slag to such a point that itbecomes non-conducting, or becomes conducting only unof oversubstantially the whole surface of the plate.

Cooling water is directed .to and -withdrawn from the furnace shell 21by means of water connections 54 and 5| (Figure`2). the upper ends ofthese connections being supported in a suitable frame 53. Each of theinsulated water jacket inserts 40, 4|, 42 and-4331s provided with twoflexible copper metall hose sections, indicated in Figures 2, 4, and 7at 54 .and 55. These sections serve not only to supply water .to each ofthe water jacket inserts but also to conduct the required electricalcurrent .to or from the water jacket inserts. A frame 53 is provided ateach side oi the furnace |0 and supports the upper ends of the flexiblecopper metal hose sections 54 and 55. Bus bars 10 (Figure 2) areelectrically connected with the copper hose sections adjacent the pointswhere the latter are supported on the frames 53, and at .the same pointsuitable water pipes 12 (Figure 8) are connected through supporting andinsulating sleeves 13 carried on the frame 53. The water supplyconnections include pipes 14 leading to a supply main 15. Obviously, ofcourse, other forms of supply, both as to coolingnwater and electricalcurrent, may be employed where desired. Also, while I- have shown onlytwo jacketed electrodes on opposite side walls for purposes ofillustration, a. greater number is preferably used. `Since the Vcoolingwater lcarries away a great :deal of heat, which reduces the der arcingconditions over a small area instead thermal efficiency of the furnace,I ,prefer tol make the furnace small,'so that the water cooled surfaceswould also be smal1, and arrange to Asurrply a relatively large amountof power for such a small sized furnace, so that the percentage of thetotal energy input that is lost in the cooling water will be as small aspossible.- One embodiment of the furnace which I have just described hasa capacity of about 700 to 800 pounds of molten material, can .take upto 100 kilowatts of electrical power input, and has a loss whenoperating between 2400 to 2600 F. of about 25 kilowatts in the watercooling. Losses other than in the cooling Water do not amount -to morethan twoAor three kilowatts.

The furnace I0 is mounted for tilting move-Y ment on the frame |2 sothat the furnace may be tilted for discharging its load of molten coalash. As best shown in Figure 3, the end wall2| of the furnace III isprovided with a pouring hole 30 provided .wi-th a spout 8|, and as bestindicated in Figures 1 and '3 the furnace includes a. trunnion shaft 85which`is mounted in bearings 35 and 31 forming a part of the supportingframework I2. The shaft 85 passes close to the pour,- ing spout 5|, andas indicated in Fig-ure l3 .the curvature of the lower wall of thepouring opening 30 and the adjacent portions of the spout 3| issubstantially arcuate about the axis-of the trunnion shaft l5. The frameor pedestal l2 is of more or less conventional construction, being builtup of angle irons welded, or otherwise fastened Itogether and secured tothe floor by any suitable means, such as lag screws or expansionframework |2 so as to support the furnace Il in level position. Thefurnace itself carries a quady rant |40, best indicated in Figure 8,which is secured to the furnace shell in any suitable manner, such as by4angle irons |0| or the like, and the quadrant |40 is preferably, butnot necessarily, made up of a section of tubing split longitudinally andbent to the proper radius.

' plunger 20 and shift the furnace |0 from the the other.

A tilting cable |05 is fastened at its lower end to/the forward portionof quadrant |00 and at its upper end is connected to a cable |06 passingover a sheave |01 and extending downwardly to a xed point |08. Acounterbalancing cable l|0 is also fastened to the flexible section |05and passes over suitable pulleys.||2 and ||3 where the end of the cableI0 supports a counterweight H5. The sheave |01 is carried at the lowerend of a plunger |20 which passes into a cylinder |2| which has suitableconnections |22 to a source of fluid pressure. By suitable controls,pressure may be directed into the cylinder I2| to raise the positionshown in Figure 8 in full lines to the position shown in dotted lines,tilting the furnace about the axis of the shaft 85. Molten materialwithin the furnace I0 will therefore be poured out of the spout 8|.

As best shown in Figure l, a steam supply connection I3 0 leads to ablowing nozzle |3| disposed at one side of the stream issuing from thepouring nozzle 8|. The rate of flow of the blowing fluid, such as steamunder pressure, and the rate of tilting of the furnace are so controlledthat the fluid pressure blows the entire molten stream laterally, as at|32, forming the product commercially known as mineral wool.

The bus bars 10 are connected in any suitable' manner with a source ofcurrent and suitable controls serve to maintain a flow of current,providing that the furnace contains molten slag or coal ash, from onepair of contacts or plates to It was mentioned above that the viscosityof a molten oxide bath is directly related to its electricalresistivity. By the use of suitable electrical controls, the resistanceof the slag in the furnace may be maintained constant and by virtuethereof the viscosity of the mass of molten material in the furnace willalso be maintained constant. This is an important feature of the presentinvention, for it is the viscosity of the slag at the time the slagencounters the blast from the blowing nozzle or other wool forming meansthat is one of the most important variablesV determining the quality ofthe mineral wool. The above mentioned controls are so arranged that ifthe resistance of the slag between the paths of contactor platesincreases, an increase in power will immediately reduce the resistance,for the higher the temperature of any I molten oxide bath, the lower itselectrical resistance becomes. On vthe other hand, if .the resistanceacross'the two sets of contactor plates falls, a lowering of the powerinput will immediately permit the' s1ag bath to C001 oir slightly sothat both its resistance and viscosity will again increase.

One of the important advantages of using molten coal ashes, entirelyaside from their availability as a by-product of no value at the presenttime, is that the mineral wool produced from coal ashes contains anappreciable percentage of iron oxides and is much softer than theordinary commercial rock wool in which the basic constituent isycomposed practically wholly of the lighter metal oxides, as for example,calcium oxide and magnesium oxide. The molten material containingbasicoxides in which the major portion is madeup ofiron oxides will bestflow freely `tabout a temperature of 2400 F., and if blown at thistemperature the best results are secured, the fibers .being soft andexible and have an average diameter, I have found, of from approximatelythe following analysis:

Per cent Silica, S102 39 Alumina, A1203 15 Lime, CaO 6 Magnesia, MgO 1Iron oxides, FezOs and FeO 37 Other oxides 2 in heating and blowing ofthe molten material.' While it is true that to 5% sulfur, and it wouldseem that the coal ash many coals may contain up coming from the furnacemight also contain appreciable quantities of sulphides, yet, however,this is not the case, for sulphides are stable only under reducingconditions and in basic slags, whereas a-boiler furnace is a fueloxidizing, not reducing, apparatus. For this reason, since practicallyall commercial coal ashes form acid, rather than basic slags, such small`amounts of sulfur as may initially enter the slag are rapidly driventherefrom.

Thus, according to the present invention, I am enabled to take a. Wasteby-product, that is, molten coal ashes which is not only of little or novalue at the present time but is usually an item of expense on accountof the need for disposal thereof, and convert this waste by-product intoa highly' useful and valuable by-product in the form of a mineral woolof uniform quality and superior characteristics, and at a cost far lowerthan any of the present methods for making a similar grade of mineralwool. Specifically, due to the use of a heat-controllable intermediatefurnace forholding and conditioning the molten raw material placedbetween the melting furnace and the blowing nozzle, I am able to controlthe uniformity of the product Without any appreciable time lag and muchmore accurately and continuously than it has been possible to do in theprevious state of the art.

Figures 9 to l5 illustrate a modified form of electric furnace embodyingcertain improvements over the furnace shown and described above.

Referring now more parfzularly to Figures 9, 10 and 1l, my second formof coal ash slag conditioning furnace is indicated in its entirety bythe reference numeral and comprises a suitable framework |5| (Figure l1)thatincludeshorizontal and vertical angles |52 andl|53 (Figure 15) andassociated side and end plates |54 and |55, the latter enclosing thefurnace bottom |56 which consists of suitable refractory blocks similarto the furnace bottom 24 described above. The sides and ends of thefurnace proper are indicated at |58 and |59, respectively, the sidewalls |58 aring upwardly, as best shown in Figure 12, while the endwalls |59 are generally parallel and vertical. The bottom |56 of thefurnace is concave and is provided with an outlet |6| through which anymolten metallic iron may be withdrawn.v

Normally the outlet |6| is closed by a plug |62 as described above inconnection with Figure 3.

The upper part or head of the furnace is indicated at |65 and comprisesan arch |66 or roof formed of refractory brick or blocks and anenclosing sheet metal shell |61 having side and end plates |68 and |69of the desired configuration. The end plates |69 of the furnace head orroof are preferably tied together by through bolts |1|, and the furnaceroof is provided with a single opening |13 through which the molten slagfrom the boiler flows into the interior of the conditioning furnace.'I'he-lower edges of the furnace roof or head |65 is defined by a pairof angles |16. The section of the furnace that receives the charge ofmolten slag is indicated at 80, and from Figures 11, 12 and 14, it willbe seen that the side and end walls |58 and |59 of the furnace areprovided with water jackets |82 and |83, respectively. Water iscirculated through the water jackets |82 and |83 by inlet and outletconnections |81.

Interiorly of the water jackets |82 and |83 the side and end walls |58and |59 consist of insulating brick |85, and interiorly of the` brick|85 each wall has a layer of refractory material |86, preferably chromeore or the like. The forward edge of the furnace roof is provided with awater conduit |88 set in suitable insulating material |89, such aschrome ore, and is connected at its ends Within the insulating material|89 to short pipe sections |9| and |92 (Figures 9 and 14). 'I'he conduit|88 does not extend the entire length of the roof but only adjacent andjust beyond the pouring spout which will be described later.

The cooling water is supplied through avpipe |95 (Figure 10), theforward end |95a of which is connected by an elbow. |96 to a coupling|91 which is connected by a short pipe |98 to the section |9| (Figure 9)Cooling water which enters through the supply |95 passes through thesections |98 and |9| and through the conduit |88, to the other section|92. From this point the water passes through a short pipe a coupling202, and anl elbow 203 to a discharge pipe 204 (Figure 11) whichoccupies approximately the same position at the right hand end (Figures9 and 11) of thefurnace that the pipe |95 occupies at the left end ofthe furnace (Figures 9 and 10).

'I'he normal slag level is indicated in Figure 14 by the referencecharacter L, and pivotally mounted above this point is a water cooledtubular slag skimmer, indicated in its entirety by the reference numeral2|0, the purpose of which is U-shaped configuration, having anintermediate section 2| and end or trunnion sections 2|2'and 2|3journaled in suitable bearings 2 I4 (Figure 15) in the form of a fibretube 2|4'a disposed Within a sleeve or pipe section 2|5 welded to theside walls of the water jacket |83. Loosely packed asbestos rope 2|6 isdisposed about the inner end of the tube 2|3 to protect the bearing fromthe heat and corrosive action of the molten slag, and the fibre tube2|4a serves to insulate the slag skimmer 2|0, which is in contact withthe slag through which current is flowing, from the end walls |59 of thefurnace. 'Ihebearing construcllevel in the furnace.

tion for the other end of the slag skimmer is identical with that justdescribed, so that a further description is unnecessary. Each end of thetrunnion sections 2|2 and 2|3 is threaded, as at 2|1, and carries avcounterweight arm 2|8 fixed thereto in any suitable manner. Each arm isprovided with a plurality of holes 2 9 (Figure 12) to receivecounterweights.

The slag skimmer is generally of tubular construction and vthe trunnions2|2 and 2|3 are similar, thereby providing for a flow of cooling fluidthrough the slag skimmer. An elbow 225 is secured to the outer threadedend 2|1of each of the skimmer trunnions 2 |2 and 2|3, as best shown linFigures 9 and 10. A flexible hose 226 is connected to a fitting 221 thatis carried by the elbow 225, the other end of the flexible hose 226being connected to an elbow 229 which forms a part of a conduit 230. Thelatter is connected by a valve 23| to the water supply pipe 95 (Figure10) at the left end of the furnace (Figure 9). The flexible tube 226 andassociated pipe 230 at the right hand end (Figure 9) of -the furnace areconnected by the associated valve 23| to the discharge pipe 204. Thus,by opening both of the .valves 23| a flow of cooling water is directedthrough the slag skimmer, the flexible hose sections 226 accommodatingswinging movement of the slag skimmer in response to changes in liquidThe flexible tubes 226 are preferably made of rubber or other suitablematerial so as to electrically insulate the water pipes from the slagskimmer.

In the type of furnace shown in Figure 4 and described above, theelectrodes by which current is passed through the mass of molten slag inthe furnace for the purpose of maintaining its viscosity constant at thedesired value are arranged in diverging relationship, the upperelectrodes being further apart than the lower electrodes, as' will beclear from Figure 4. This results ina construction in which the path ofthe current between the upper electrodes is longer than the path betweenthe lower electrodes. According to the form of invention shown inFigures 9 to 14, the current paths between the pairs of electrodes areall of the same length, due to the fact that the electrodes are arrangedin vertical parallel planes, as best shown in Figure 11. Also, the formof electrode shown in the latter figure is simplified in certainrespects as compared with the electrodes shown in Figures 4 and 7.

Referring now more particularly to Figures 11, 12 and 13, it will benoted that there are six electrodes at each end of the furnace and thatthe electrodes are arranged in three rightand left-hand pairs. As bestshown in Figure 13, each electrode, indicated by the reference numeral250, consists of an inner metallic contact plate to the central portionof which a conducting bar 252 is firmly secured, as by Welding or thelike. The plates 25| m-ay be made of any suitable material butpreferably they are madeof wrought iron. A rectangular shell 253 is ingenerally marginal registration with the contact plate 25| and isprovided with inner and outer walls 255 and 256, which are spaced apartto form a Water jacket 251 having a water chamber 258. Between the innerwall 255 of the water jacket 251 and the contact plate 25| is a mass ofheat insulating material 259, preferably in the form of heat insulatingbrick. The conducting bar 252 extends outwardly from the .contact plate25| through an opening formed by a sleeve 26| welded in openings in thecentral portions of the plates 255 and 256. The outerend of the bar 252is threaded and receives an attaching nut 262 by which the electrodeparts are held together. A current-carrying cable 265 is provided with aterminal 266 which is bolted, as at 268, to the outer end of the bar252. A short intermediate wall 21| is secured to the water jacket walls255 and 256 in any suitable manner, as by welding, the ends beingattached to or disposed closely against the sleeve 26| and the oppositeedge ofv the electrode. By virtue of the short plate 21|, the Waterchamber included in each of the electrodes is generally U-shaped inconfiguration.

A pair of short bushings 213 and 214 extend through suitable openings inthe outer electrode plate 256 and extending into the water space onopposite sides of -the wall 21|, thus communicating with the legs of theU-shaped water chamber. A pair of return bends 215 and 216 andassociated sleeves 211 and 218 are provided, thel lower return bend 215connecting the upper bushing 213 of the lower electrode to the lowerbushing 214 of the intermediate electrode. Similarly, the return bend216 connects the upper bushing 213 of the intermediate electrode to thelower bushing 214 of the upper electrode. In the lower electrode, thelower bushing 214 is connected by a pipe or hose 219 to a suitable watersupply. Water enters through the lower bushing 214 of the lower unit,passes around the U- shaped passage therein, through the return bend215, and again through the U-shaped passage of the intermediateelectrode. 'I'he upper bushing 213 of the upper electrode is connectedto a suitable outlet or. discharge pipe 28|. Thus, Water flowing inthrough the intake 219 passes from one electrode to another in serialarrangement and in a generally sinusoidal path.

The direct contact of the plate 25| with the periphery of the shell 253and the connection of the plate 25| with the water jacket 251 throughthe bar 252 provide for such an amount of heat transference from thecooling water chamber to the contact plate that the latter is notoverheated, but at the same time the insulation 258 prevents too rapidheat transference, so that the slag adjacent the contact plate does notbecome chilled and frozen. If the slag at the contact plate 25| freezes,then the mass of slag acts as an insulator and prevents the proper flowof current.

'I 'he three pairs f electrodes at each end of the furnace are mountedin an opening 285 defined by three angle bars 286, 281 and 288 in thefurnace end. The insulation 259 is placed not onlyV between each of thecontact plates 25| and the associated water jacket 251, but also betweenthe inner portions of the shells 253 and the insulation |85 and |86around the opening 285. As best shown in-Flgure 13, the angle bars 286,281 and 288, which define a wall of the water jacket |83, extendoutwardly of the opening 285 and are provided with bolt receivingapertures 289. Each of the electrode units carries four strips 29| ofinsulating material which is secured thereto by countersunk bolts 292 soas to form a part there` of. The several insulating strips are bolted,as atv 295, to the angles 286, 281 and 288, therebyI securing theseveral electrode units in place. The electrode construction at`theother end .of the furnace is substantiallythe same, so that a furtherdescription is unnecessary.

The operation of the furnace so far described is substantially the sameas the furnace shown in Figures 1 to 8. The molten coal ash slag fromthe boiler is directed into the furnace through the roof opening |13 andheld in the furnace at the desired temperature and viscosity, under thecontrol of suitable electrical control apparatus associated with theelectrodes. Cooling water is directed through the 'furnace jacket by thepipes |81, and through the electrodes by-the pipes 219 and 28|. Currentflowing from one set of electrodes at one end of the furnace to theelectrodes at the other end, under suitable control, maintains the massof molten slag at the desired temperature, the relation between theconducting bars 252 of the electrode and the insulating material 259being such that the electrodes are kept cool enough to prevent corrosionand destruction but not so cool that there is any tendency for the slagto freeze and hence set up a mass of insulation interfering with theproper operation of the furnace. C

The furnace shown in Figures 9 to 15 may be mounted for tilting movementabout an axis in Athe saine Away as the furnace shown in Figures 1 to 8,or it may be mounted upon a suitable framework having curved trackwaysproviding for the tilting movement of the furnace. Whatever the methodof support, it is desirable to have the furnace tilt about an axis thatpasses through provided novel spout construction and novel heating meansassociated therewith, which will now be described.

Referring now more particularly to Figures 9, 10, 14 and 15, one sidewall of the furnace is provided with a spout opening or tap hole 30|(Figure 14) underneath the water pipe section |88 in the furnace roof,as described above. Around the tap hole 30| is mounted a spout frame 305which consists of suitable angle bars 306 and an enclosing shell 301,preferably made of sheet metal or the like. The shell 301 includes apair of en'd boxes 308 formed of stainless steel or the like. The spoutframe and shell enclose two pairs of spout channels 3|2 and 3| 3formedin suitable refractory material contained within and supported bythe spout frame. Each pair of channels 3| 2 and 3| 3, as best shown inFigure 15, are arranged generally parallel but in diverging relationwith respect to the corresponding channels of the other pair. 'I'hechannels are covered by refractory brick 3|'5 or other insulatingmaterial, and at their upper ends the channels 3|2 and 3|3 are divi-dedby a block of Carborundum tile 3I1 set on a steel block 3| 8 adjacentand above the slag level L and embedded in suitable refractory material,such as chrome ore. At this point it will be noted that the upper edgeof the water jacket |82 defines a knife edge 3|9 over which the slagpasses whenl the furnace is poured. The outlet ends of the channels 3| 2an'd 3|3 are directed downwardly, as at 32| and 322, being enclosed bythe end box 308 at this .point The molten slag is thus dividedv intofourdivergent streams from the tap hole 30| and didesired temperature as itleaves the tap hole 30|Y 4 proper temperature, thei'runner delivers theslag and is discharged onto the spinning discs, I provide suitableheating means, preferably in the form of gas burners or the like mounteddirectly on the furnace adjacent the tap hole 30|. To this end, suitablebrackets 325 an'd 326 (Figure 9) are mounted on the furnace roof andsupport clips 321 and 328 on which a bar 329 is carried. The bar 323serves to support four gas conduits 33|, 332, 333 and 334 whichcommunicate with a manifold 335. '.I'he manifold 335 is closed beyondthe conduit 334 and at the other end communicates with an elbow 331which is carried at the upper end of a gas supply pipe 336, the latterbeing supported by a U-bolt 339 which is fastened to the downwardlyturned end 34| of the supporting bar 329.

Each of the gasA conduit sections 33| to 334 carries a nozzle 345 at thelower end. The nozzles 345 are disposed above corresponding openings 341formed in the insulating covering 3|5 over the channels 3 I 2 and 3|3and are so set as to direct the gas flame substantially to the knifeedge section of the spout over which the molten slag flows.

Each of the nozzles 345 includes an air tube 35|' which receivescompressed air from an associated air pipe 352 supported above theconduits that feed gas to the nozzles. Each of the air pipes 352 isconnected at its upper end by an elbow to an associated air line 353,the air lines 353 being supported by asuitable bracket 358 bolted to thesupporting bar 329 individually controlled by suitable Valves (notshown). It will be noted that the air nozzles are directed toward theslag streams. The effect of each of these several air blasts is toretard the flow of the associated slag stream, both by mechanicallyopposing the iiow and also by` lowering the temperature of the gas flameand the slag, making the latter more viscous and decreasing its flow.Thus, by governing the amount of air which passes through the variousnozzles, the flow through the several slag channels 3|2 and 3|3 can becontrolled easily and accurately, so as to have the quantity of slagdelivered to the spinning discs by all of the slag streams substantiallythe same.

Another gas conduit 36| leads downwardly (Figure -10) to a manifold 362supported by a bracket 363 across the side of the furnace underneath thespout frame 305, as best shown in 362 are attached a. pair of laterallyelongated gas nozzles 364 connected to the gas main by a pipe ysection365. The gas manifold 362 also has a pair of v-individual nozzles 361underneath the elongated nozzles 364, the nozzles 361 being connected bysections 368 to the gas main 362. The lower nozzles 364 and' 361 are set so as to direct the.

flame at the point where the slag stream leaves the exit ends of thechannels 3|2 and 3|3.

From the above description it will be seen that the furnace shown inFigures 8 to 14 is constructed so that the molten slag, as it is. poured'from the furnace, vis divided into four streams in diverging relationand discharged onto a pair of spinning discs while under exacttemperature conti-01 due not only to the controlled flow of current fromone set of electrodes to the other but also due to the application ofthe desired or required amount of heat to the slag stream both beforeand after it is divided.

The electric furnace construction described above includes or isprovided with means for receiving the molten slag as it iiows from theboiler and, while maintaining Athe boiler slag at the at the proper ordesired temperature conditioning furnace.

From the above it will be apparent that I have provided a furnaceconstruction particularly adapted for handling molten coal ash slag andarranged to receive the molten slag from a furnace and to maintain theslag at all times in the proper condition for forming mineral wool.Obviously, my invention is-not to be limited to the particular detailsshown and described, as widely different means may be employed in thepractice of the broader aspects of my invention.

What I claim, therefore, and desire to secure by Letters Patent is:

1. A furnace for maintaining a mass of nonmetallic material in themolten state, comprising a container having walls of refractorymaterial, a pair of contactor plates disposed against the inner surfaceof opposite side walls, a cooling water jacket disposed on the outsideof each of said side walls,refractory material having low heatconductivity disposed between said jackets and said plates, and heatconducting bars connected electrically with said plates and saidjackets.

2. A furnace for maintaining a mass of nonmetallic material in themolten state comprising a container having walls of refractory material,a pair of contactor plates disposed against the inner surface ofopposite side walls, a cooling water .jacket disposed on the outside ofeach of said side walls and electrically insulated from one another, andheat conducting bars connecting each of said plates with the associatedwater jacket, the bars being formed to secure a predetermined rate ofheat transfer between said plates and cooling jackets.

3. In an electric furnace, an electrode comprising a contact plate,cooling means spaced therefrom, refractory insulating material disposedbetween said cooling means and said plate, and heat conducting meansconnecting said cooling means and said plate to secure the desired rateof heat transfer therebetween.

into the 4. In an electric furnace an electrode comprising a contactplate, cooling means spaced therefrom, refractory insulating materialdisposed between said cooling means and said plate, heat conductingmeans connecting said cooling means and said plate to secure the desiredrate of .heat transfer therebetween, and current conducting meansconnected to said cooling means, said heat conducting means serving alsoto carry current from said cooling means to said contact plate.

5. In an electric furnace, a composite Water cooled electrode comprisinga contact plate, a water chamber, and two masses of material betweensaid plate and chamber, one being conducting material and the other aninsulating material, and proportioned with respect to each lother thatneither the plate is overheated nor the molten material frozen atA theelectrode. l

- 6. A furnace for maintaining a mass of nonvmetallic material in themolten state comprising a container having walls of refractory material,a pair of electrodes on the inner surface of opposite` side Walls ofsaid container, insulated-water jacketson the exterior thereof, acurrent carrying cable connected to each o f said water jackets,

and conducting bars joining each of said elec-y trode comprising meansforming a water chamber, inlet and outlet conduit means associatedtherewith, a contact plate spaced from said water chamber, meansestablishing a limited amount of thermal and electricalconductivity'between said plate and chamber, heat insulating materialsurrounding said last mentioned means, and attachv ing means for saidwater chamber in the form o1' dielectric members secured to saidchamber.

8. In an electric furnace, a composite water

